There is mounting interest and concern, both in the scientific community and in legislative and regulatory bodies, about the psychiatric effects of anabolic-androgenic steroids. These drugs, used illicitly by hundreds of thousands of Americans, may produce substantial psychiatric morbidity in some individuals, and may also display significant abuse potential. Thus, steroid use represents a potentially serious public health problem. To date, however, most laboratory studies of steroids have used only modest dosages of the drugs; thus, information on their psychiatric effects comes largely from naturalistic studies which have relied almost exclusively on retrospective self-reports of athletes taking uncertain doses and combinations of drugs obtained illicitly. The proposed study attempts to overcome these limitations by assessing in detail the psychiatric effects of up to 600 mg per week of testosterone cypionate, a widely abused steroid, administered in a placebo-controlled, double-blind crossover design. The study uses gradually increasing doses of the drug, together with frequent and extensive monitoring of medical and psychiatric effects, to protect the safety of the subjects. Psychiatric effects of testosterone administration and testosterone withdrawal will be monitored via four rating scales administered weekly, and by daily diaries completed by the subject himself. In addition, the investigators will obtain weekly diaries from a "significant other" who knows the subject intimately, and who can observe his behavior. Physical and laboratory measures, including neuroendocrine measures, will be conducted at intervals throughout the study, both to assess potential adverse medical effects of testosterone, and to determine whether neuroendocrine changes may predict psychiatric effects. In summary, the proposed study is expected to provide psychiatric data which is more reliable and more extensive than that obtained from previous naturalistic or laboratory studies of steroid effects.